To quantify N2O fluxes between soil and atmosphere and understanding those processes driving them, is crucial if we aim to reliably predict one of earth's important greenhouse gases' origin and fate. Soil moisture has been identified as one major driver of N2O fluxes, drought has been observed to decrease soil N2O emissions and accounts for soil N2O consumption. We monitored N2O fluxes occurring at the soil/atmosphere interface of three temperate deciduous Korean forest sites experiencing a pronounced early summer drought followed by heavy East Asian monsoon rains. Because soil texture can enhance or mitigate soil drought effects, we selected sites which were different in topsoil texture. Therefore, we took closed chamber measurements of N2O fluxes during the growing season 2010 and determined N2O concentrations and δ15N values along soil profiles in the dry and monsoon season for a sandy-loam site. We observed N2O consumption at all of our study sites during early summer drought, which turned into N2O emission during the monsoon season. The N2O balance of the sandy-loam site remained slightly negative during the entire vegetation period. Soil moisture explained most of the measured N2O fluxes. For a sandy-loam forest soil we calculated a switch between N2O emission and consumption at an intermediate soil moisture (pF level of 3.02) which corresponds to a water filled pore space (WFPS) of 36%, but at half an order of magnitude moister soil (pF level: 2.57; WFPS 50%) at a loamy site. N2O concentration and δ15NN2O values along the soil profiles suggest that those processes driving the N2O fluxes at the soil/atmosphere interface most likely occurred in the topsoil. Our results contribute to our knowledge on the global N2O budget, because monsoon affected forests cover large areas worldwide and their soils' N2O emissions have so far been uninvestigated.
Bibliographical noteFunding Information:
This work is part of the research group “TERRECO – Complex TERRain and ECOlogical Heterogeneity” and financially supported by the German Research Foundation (DFG) . We thank Juyoung Seo and Inyoung Jang for supporting us in the field, for taking care of sample logistics in Korea and for providing us with required equipment. We thank Sebastian Arnhold for providing data on soil texture and Steve Lindner for his help in the field. We are thankful to Peng Zhao for his patient assistance by removing millions of fine roots out of numerous soil samples by hand, and to Isolde Baumann and Christine Tiroch, who were of great assistance to us by measuring isotope abundances. We furthermore acknowledge the farseeing, careful and very professional coordination of the TERRECO fieldwork by John Tenhunen.
All Science Journal Classification (ASJC) codes
- Soil Science